The invention relates to an apparatus comprising a clamping mechanism for coupling an exchangeable element to the apparatus in a predetermined angular orientation.
The invention is particularly applicable to an exchangeable element which is comparatively heavy and which must be coupled to the apparatus, for example, by manual manipulation. In such a case it is often advantageous if first a comparatively loose connection can be made between the apparatus and the exchangeable element, so that the element at least cannot fall off. To this end, the coupling mechanism often comprises a bayonet coupling. A slight rotation of the element with respect to the apparatus is usually sufficient to establish the loose connection.
Known apparatus often comprise a clamping mechanism with a clamping force which acts against the rotation, and the element is assumed to be adequately secured in the correct position thereby. This arrangement has several drawbacks. For example, a comparatively large torque is exerted on the apparatus, there usually is no certainty that the elements has been rotated far enough, and the element could shake loose during operation and even fall off the apparatus. A snap-type clamping mechanism which is activated after sufficient rotation of the element can prevent the element from shaking loose, but such a mechanism does not prevent excessive torques and does not always ensure with certainty that the element has been rotated far enough. Similar undesirable torques occur again, of course, when the element is removed.
It is an object of the invention to provide a clamping mechanism which assures correct positioning of the exchangeable element, which assures that the exchangeable element will not fall off, and which avoids the application of excess torques. According to the invention the clamping mechanism comprises at least one folding hand grip which can be folded down to lock the clamping mechanism with spring pressure only when the element has a predetermined orientation with respect to the apparatus.
With this clamping mechanism it is not necessary to exert a large torque, because the element may remain comparatively loosely attached to the apparatus until the coupling is engaged. The risk of the element not being rotated far enough is thus substantially reduced. When the clamping mechanism is provided with means which allow the hand grip to be folded down only in the engaged position of, for example, a bayonet coupling, insufficient rotation is fully precluded and the correct orientation of the hand grips can be visually checked. For example, by releasing a spring force in the bayonet coupling when the grip is folded down, a clamping coupling is obtained in the correct position.
The hand grip in a preferred embodiment of the invention comprises at least one preferably slightly conical guide pin or bore, and the apparatus comprises a matching bore or guide pin. The clamping effect is produced in a preferred embodiment by a leaf spring which is secured to the apparatus and which ensures that the coupling clamps firmly when the hand grip is folded down.
The clamping mechanism of a preferred embodiment of the invention comprises two symmetrically arranged folding hand grips which lie in planes extending transverse a coupling surface of the apparatus in the unfolded or erected position. The hand grips lie in planes parallel to coupling surface in the folded position.
The element can be coupled in two axial orientations in a further preferred embodiment because each of the grips has a symmetrical construction. This embodiment is attractive, for example, for coupling a collimator to a gamma camera. Such collimators are sometimes of a focussing type, which means that the channels of the collimator are all directed onto one point or line. The coupling mechanism enables such a collimator to be fitted so that it has either a converging or a diverging effect.